Created simplified Easing/Tweening system

Added a tweens package to hold tweens.
Added BlockStartLevel to handle level start animations for blocks.
Added a Tween abstract class to form the basis of all future tween
classes
Added a BodyPositionTween class to handle body position easing.
Added a ScaleTween class to handle scale easing.
Added a SimpleEasingStrategy class to simplify how the easing system
works. One single method is all that is necessary now (ease()).
Added an enum EasingDirection to work with the SimpleEasingStrategy
class.
Added some easing methods to the game paddle.